U-cup radial seals have been used for many years in high pressure applications, such as hydraulic cylinders, suspension struts and the like, to seal around the reciprocating rods of such cylinders or struts and prevent the escape of hydraulic fluid. Such U-cup seals come in many shapes and styles and have included separate elements that have contributed to their sealing ability. For instance, some use separate energizer springs, in the form of rubber O-rings or the like. Such rubber springs are typically located between the legs of the U-cup seal. Because such rubber O-ring springs are exposed to the hydraulic fluid in the cylinder, the selection of rubber material is dictated by its compatibility to the hydraulic fluid. As a result, its functional characteristics as a spring may suffer in such selection. Also, dynamic pressures on and movements of the seal can dislodge the rubber spring from its intended position and reduce its effectiveness. Other U-cup seals have been utilized with separate anti-extrusion rings, which are intended to prevent the seal lips of the seal from extruding into the annular gap between the cylinder rod and the cylinder housing or head as the result of the high pressures in the cylinder or the reciprocating movement of the rod. However, such separate anti-extrusion rings may be assembled in the wrong location or inadvertently left out during assembly. Other U-cup seals are provided with two axially spaced seal lips. High fluid pressure may become entrapped between these two lips. This can result in fluid loss due to leakage past the second seal lip on the non-pressure side of the seal.
The present invention is directed to overcoming shortcomings of the prior U-cup seals with respect to separate components to obtain improved sealing performance and to fluid loss problems.